Syntheses of the macrolide antibiotic methymycin, the ionophore boromycin, and the cytostatic agent verrucarin A will be pursued. The methymycin synthesis will employ a route already developed in our laboratory to the Prelog-Dierassi lactonic acid, and will be directed toward the aglycone methynolide prior to coupling with the desosamine residue. The work on boromycin will be targeted towards resolution of the subunits of this molecule which have been prepared in racemic form. Coupling of the four segments, incorporation of the borate complex, and lactonization will constitute the final stages of the synthesis. The approach to verrucarin A will continue to explore a route to verrucarol, the parent nucleus of this family of macrocycles, using a ring expansion to construct the bridged bicyclic moiety in this structure. Synthesis of the dicarboxylic acids, corresponding to the macrolide loop of the verrucarins, will also be investigated.